The manufacture of external timepiece components is often accomplished using noble metals, such as gold or platinum, so as to ensure excellent resistance to corrosion. However, these metals are of high density, and the timepieces thereby made, particularly watches, are very heavy for the user, and are also expensive. A material such as gold is malleable, and it has average mechanical qualities, which often means that it is necessary to select gold alloys, which are more resistant, but also more susceptible to corrosion, with variations in appearance over time.
JP Patent Application No 60228666 A in the name of CITIZEN describes the brazing of components made of gold or gold alloy on a base made of titanium or titanium alloy. This method uses a TiN surface obtained by nitriding to stop the gold penetrating the titanium, and pre-forms a Ni—Pd or Ni—Cu layer.
FR Patent Application No 926715A in the name of PEDERSEN discloses a damascene process with the prior creation of a groove in a first component, which is brought to a temperature higher than the melting temperature of a filler metal forming a decoration, before depositing or colouring the filler metal in the groove in the melted state. Given that the temperature is not necessarily raised above the melting temperatures of the metal of the first component and of the filler metal, this is brazing. The assembly can be shaped by drawing after assembly and brazing.
CH Patent Application No 264968A in the name of BOITES LA CENTRALE discloses the fixing by brazing of a noble metal shell to a base metal support part.
GB Patent Application No 1406909A in the name of SUWA SEIKOSHA discloses the covering, by a spraying technique, with a coating of metallic or non-metallic material, of a basic body which may be made of titanium.
CH Patent Application No 30607A in the name of THIEBAUD discloses a plated watch case, with a non-precious metal part plated with gold leaf on both sides, whose edges are provided with a flat solid gold rim, entirely concealing the base metal. This flat rim is welded to the edge of the plating.
CH Patent Application No 652560A in the name of PRECIMAX discloses a watch bezel in two parts, the lower part made of titanium, the upper of gold, mechanically assembled to each other.
CH Patent Application No 632377A in the name of GRANDJEAN discloses another method similar to damascene, in the specific case of a stainless steel support, in which a hollow is made. The temperature of the support is raised to a temperature close to the “ideal welding temperature” of the stainless steel concerned, and higher than the melting temperature of an ornamental metal, typically gold, which is deposited in the hollow in the form of solid fragments, the ornamental metal then melting and filling the hollow, thereby forming a braze.